The present invention relates to Al alloys for a welded construction, which alloys are excellent, particularly in welding characteristics, in addition to general characteristics, such as mechanical strength and bending processability. The present invention also relates to welded joints using the Al alloys for a welded construction, which are used in automotive frames, bodies, and other parts requiring lightweight, inexpensive and high-mechanical strength welded joints.
In the specification and claims, all compositions of Al alloys are meant to be expressed in % by weight, which is referred to simply as %.
Hitherto, cold-rolled steel sheets have been mainly used in automobiles. However, the demand for lightweight automotive bodies has increased in recent years from the viewpoint of reducing fuel consumption for automobiles, and use of sheets-(or plates) and extruded materials of Al alloys, in place of steel sheets, is being studied and is actually used in some parts.
Such Al alloy sheets are required, as automotive materials, to have excellent press workability, high mechanical strength, high weld strength, excellent corrosion resistance, etc.
The Al alloy extruded materials are required to have excellent bending workability, high mechanical strength, high weld strength, and excellent corrosion resistance.
As Al alloy materials meeting such requirements, Alxe2x80x94Mgxe2x80x94Si series alloys (6000 series alloys), such as 6061 alloy, and Alxe2x80x94Mg series alloys (5000 series alloys), such as 5052 alloy, have been used in sheet materials, and Alxe2x80x94Mgxe2x80x94Si series alloys (6000 series alloys), such as 6061, 6N01, and 6063 alloys, have been used in extruded materials.
However, the 6000 series alloys and 5000 series alloys described above lack satisfactory mechanical strength, and particularly, their welds (welded joints) by arc welding are poor in mechanical strength.
The objects of the present invention that are described above have been achieved by the following means:
(1) An Al alloy for a welded construction having excellent welding characteristics, wherein the Al alloy comprises 1.5 to 5% by weight of Si (hereinafter, % by weight is referred to as %), 0.2 to 1.5% of Mg, 0.2 to 1.5% of Zn, 0.2 to 2% of Cu, 0.1 to 1.5% of Fe, and at least one member selected from the group consisting of 0.01 to 1.0% of Mn, 0.01 to 0.2% of Cr, 0.01 to 0.2% of Ti, 0.01 to 0.2% of Zr, and 0.01 to 0.2% of V, with the balance being Al and inevitable impurities.
(2) The Al alloy for a welded construction according to item (1), wherein the amount of Si is from 2.6 to 5%.
(3) A welded joint having a weld (weld zone) excellent in mechanical strength, which is formed by arc-welding with an Al alloy filler metal containing 2 to 6% of Mg, a base metal being an Al alloy that comprises 1.5 to 5% of Si, 0.2 to 1.5% of Mg, 0.2 to 1.5% of Zn, 0.2 to 2% of Cu, 0.1 to 1.5% of Fe, and at least one member selected from the group consisting of 0.01 to 1.0% of Mn, 0.01 to 0.2% of Cr, 0.01 to 0.2% of Ti, 0.01 to 0.2% of Zr, and 0.01 to 0.2% of V, with the balance being Al and inevitable impurities.
(4) The welded joint according to item (3), wherein the central metal components in the weld described in item (3) comprise 0.5 to 4% of Si, 1.0 to 5.5% of Mg, and 0.05 to 1.4% of Cu.
(5) The welded joint according to item (3) or (4), wherein the weld described in item (3) after welding is heat-treated, to form a high-mechanical strength, age-hardened weld.
(6) A welded joint having a weld excellent in weld cracking property, which is formed by arc-welding with an Al alloy filler metal containing 3 to 13% of Si, a base metal being an Al alloy that comprises 1.5 to 5% of Si, 0.2 to 1.5% of Mg, 0.2 to 1.5% of Zn, 0.2 to 2% of Cu, 0.1 to 1.5% of Fe, and at least one member selected from the group consisting of 0.01 to 1.0% of Mn, 0.01 to 0.2% of Cr, 0.01 to 0.2% of Ti, 0.01 to 0.2% of Zr, and 0.01 to 0.2% of V, with the balance being Al and inevitable impurities.
(7) The welded joint according to item (6), wherein the central metal components in the weld described in item (6) comprise 2.0 to 11% of Si, 0.05 to 1.4% of Mg, and 0.05 to 1.8% of Cu.